Method for preventing air embolism in a syringe for angiographic power injector

ABSTRACT

A power injector or syringe designed for use in angiographic studies having a cylindrical, hollow housing and a plunger or piston fitted for reciprocating action within the housing. The housing is provided with a transparent, magnifying conical-shaped head for more easily detecting air bubbles entrained in a liquid contained by the syringe. Detection of these bubbles prior to injection minimizes the chances of air embolism during intravenous injections.

United States Patent Runnells et a].

METHOD FOR PREVENTING AIR EMBOLISM IN A SYRINGE FOR ANGIOGRAPHIC POWERINJECTOR Inventors: Robert R. Runnells, Fruit Heights;

Frank W. Longson, Salt Lake City, both of Utah MDT Instrument Company,Salt Lake City, Utah Filed: Nov. 1, 1971 Appl. No.: 194,747

Assignee:

US. Cl. 128/2 R, 128/218 C, l28/2.05 R Int. Cl. A6lb 5/02, A6lm 5/18FieldofSearch 128/218 R,2l8 C, l28/22l, 2l8 N, 2 R, 215, 216, 214 C, 218A, 2.05 R, 2.05 F, 2 S

References Cited UNITED STATES PATENTS [/1972 Hobbs 128/218 A Aug. 14,1973 3,349,767 l0/l967 Gidlund 128/218 R 3,030,954 4/1962 Thornton,Jr... 128/214 C 2,586,581 2/1952 Tschischeck 128/218 C X PrimaryExaminer-Richard A. Gaudet Assistant Examiner-J. C. McGowanAttorney-David V. Trask et al.

A power injector or syringe designed for use in angiographic studieshaving a cylindrical, hollow housing and a plunger or piston fitted forreciprocating action within the housing. The housing is provided with atransparent, magnifying conical-shaped head for more easily detectingair bubbles entrained in a liquid contained by the syringe. Detection ofthese bubbles prior to injection minimizes the chances of air embolismduring intravenous injections.

ABSTRACT 3 Claims, 1 Drawing Figure Pmzmuwm 3.752.145

INVENTOR. Robert R. Runnells BY- rank W. Longson Their Horney METHOD FORPREVENTING AIR EMBOLISM IN A SYRINGE FOR ANGIOGRAPHIC POWER INJECTORBackground of the Invention 1. Field This invention relates to a liquidinjector, and particularly to a power syringe or injector designed foruse in angiographic studies.

2. State of the Art Angiography is generally defined as the visualroent-. genological study of blood vessels. As the definition implies, adye or contrast fluid is continuously injected into an artery or veinuntil the fluid is distributed throughout the vascular system. X-raysare then taken, permitting the vascular system (because of the opaquequality of the dye) to be clearly outlined. Defects, constrictions, etc.of the vascular system can thereby be easily detected. The inadvertentintroduction of air during transportation of the contrast fluid into thevascular system can result in air embolism.

Power injectors are commonly used in angiographic studies. Normally,such an injector includes a syringe with a cylindrical hollow housinghaving an outlet at one end and a piston or plunger mounted slidablywithin the housing and capable of removal from the end of the housingopposite the outlet. Contrast fluid is poured into the syringe housingopening with the plunger removed. The plunger is controllably movedwithin the housing by a power means, typically, a hydraulic drivemechanism. The housing and power means are usually held in predeterminedstationary position by an adjustable support means (the syringe armhousing" of the injector). A catheter is conventionally connected to thesyringe housings outlet, and a contrast fluid is forced through thecatheter into a vascular system. I-Ieretofore, angiographic techniquesrelying upon power injectors have exposed the patient to an undesirablyhigh risk of air embolism, because of the difficulty of determiningwhether air is entrapped within the syringe.

Summary of the Invention The present invention provides an improvedangiographic syringe specifically adapted for use in conventionalangiographic power injectors. The syringe of this invention comprises aspecial magnifying head at the outlet end of the syringe housing whichfacilitates the discovery of entrapped air. The head is also speciallycontoured within to provide a safety chamber which, in cooperation withstop means, prevents the expulsion of a certain quantity of the contrastfluid from the syringe.

Brief Description of the Drawings The drawing, which illustrates what ispresently regarded as the best mode for carrying out the invention, is aperspective view of the angiographic syringe of this invention withsections cut away for clarification.

Description of the Illustrated Embodiment The syringe of this inventionincludes a cylindrical, hollow housing 12 and a plunger or piston plate14 match-fitted within the housing for slidable action. By providing anoutside wall diameter of the piston plate 14 fractionally smaller thanthe inner wall diameter of the cylindrical housing 12, substantially noliquid escapes from between the walls under normal use. However, toinsure a tight circumferential fit between the inner wall of the housingand the outer wall of the plunger (yet not overly restrictingreciprocating action of the plunger), O-rings 16 are inserted intogrooves 18 cut along the outer wall of the plunger. The sealing actionof these O-rings insures a tight fit against the inner wall of thehousing, particularly if the inner housing wall happens to be irregular.

A threaded shaft 20 is attached to the piston plate 14 and extends upbeyond the cylindrical housing 12, even when fully advanced toward theoutlet 22 of the housing 12. The shaft 20 may be either permanently ordetachably fastened to the piston plate 14. As shown, one end 20a of theshaft 20 is screwed into a corresponding threaded central opening 24 ofthe piston plate 14. The

other end 20b of the shaft 20 may be connected to the drive mechanism ofa power injector by any suitable means (not shown). The central portion20c of the shaft 20 engages a threaded cental opening 30 of a circularstop plate 32 having a diameter larger than the inner diameter of thesyringe housing 12. The stop plate 32 may be positioned at any desiredlocation along the shaft 20 to check the advance of the piston plate 14(by contact with the upper edge 34 of the syringe housing 12) as theshaft 20 is pushed down through the syringe housing 12. In this fashion,a predetermined quantity of contrast fluid, as selected by properpositioning of the stop plate, but no more, is injected into thevascular system of the patient.

In most angiographic studies the amount and rate of fluid introducedinto the vascular system by the syringe must be carefully controlled.The upper portion 36 of the syringe housing 12 is threaded for mountingwithin the syringe arm housing (not shown) of conventional powerinjectors. When so mounted, the upper end 20b of shaft 20 is connectedas described hereinbefore to a drive system capable of moving the shaftand piston plate 14 through the housing at a preselected controlledspeed, thereby insuring a constant and continuous flow of a contrastfluid from the syringe into the vascular system.

At the outlet end of the syringe housing 12 is a novel syringe head 40manufactured from a transparent material which is molded and/or machinedto achieve magnification sufficient to facilitate viewing of the fluidcontained therewithin. The syringe head 40 is preferably conicallyshaped-that is, the walls 42 of the syringe head converge in and downtoward a centraly located outlet 22. A catheter (not shown) may beconnected to the outlet 22 by means of a coupling means, such as theluer lock catheter coupling 44 illustrated, for carrying fluid from thesyringe and into the vascular system.

The interior 46 of the magnifying head 40 provides a safety chamberwhich captures and retains a residual portion of the contrast dye orother fluid even when the piston plate 14 is fully advanced toward theoutlet 22. Further advance of the piston plate 14 is checked by a stopsurface 48 defined in part by the upper edge 40a of the head 40. It isthus physically impossible to expel all of the fluid contained by thesyringe housing 12 through the outlet 22 by merely advancing the pistonplate 14. This feature, together with the magnification provided by thehead 40, makes it possible to virtually assure that no air will beinjected into a patient from the claimed syringe.

The procedure normally followed in using the claimed syringe is to firstposition the syringe housing with the outlet end up and themagnification head 40 removed. Contrast solution is poured into thesyringe housing and the head 40 is replaced. A tube is then attached tothe outlet 22 of the syringe and the free end of the tube is submergedin contrast solution. Air is bled from the syringe by advancing thepiston plate 14 toward the outlet 22. Additional contrast solution maythen be drawn through the tube into the syringe housing by retractingthe piston plate. The contents of the safety chamber 46 may then beviewed through the transparent wall 42 of the magnifying safety head. Ifbubbles are noted, the piston plate is advanced and retracted once moreto expel the entrapped air and to replace the desired volume of contrastsolution. The contents of the safety chamber are again viewed, and thepiston plate may again be advanced and retracted as often as necessaryuntil no bubbles are observed through the magnifying walls 42 of thehead 40.

Sometimes it is convenient to eliminate the step of filling the syringehousing through the tip end, but in any event, the presence of entrappedair is determined by visual observation with the magnifying head up andthe syringe as nearly vertical as possible, and after all observed airis expelled, injections should be given with the outlet down and thesyringe as nearly vertical as the angiographic procedure permits.

The piston plate is advanced in accordance with the program of theangiographic procedure, but the piston plate can never advance beyondthe stop surface 48 of the magnifying head 40. Any entrapped air willtend to rise in the contrast solution toward the piston plate.Accordingly, it will be retained within the safety chamber 46.

Although in most cases the housing is constructed from a metal such asstainless steel, durable plastic may also be used. The syringe head,although normally totally transparent, may be constructed from an opaquematerial such as plastic or metal and magnifying windows inserted intothe head to permit internal viewing.

For most angiographic work the solution introduced into the patientshould be maintained at a controlled temperature, e.g., a temperatureapproaching body temperature. The claimed syringe is compatible with theheating jackets (not shown) contained within the syringe arm housings ofavailable power injectors, but it is within contemplation that heatingcoils may be provided in the syringe housing 12 if desired.

The syringe head 40 is transparent and capable of magnification, but itmust also have high resistance to breakage and be resistant to theconditions normally encountered in sterilization procedures. Themagnifying power of the head should be substantially greater than isprovided by the glass walls of a conventional medical syringe, forexample. Thus, the surfaces of the walls 42 should be contoured toincrease the magnification provided by the shape of a conventionalsyringe tip. Transparent polycarbonate resin, such as that marketed bythe General Electric Company under the Trademark LEXAN," is thepresently preferred material of construction, but certain other plasticand resin materials have suitable properties for use.

Reference herein to details of the illustrated embodiment is notintended to restrict the scope of the claims which themselves recite thefeatures regarded as essential to the invention.

We claim:

1. In angiography wherein contrast solution is poured into the housingof a power injector syringe and thereafter expelled at a controlled rateby power means advancing the plunger of said syringe towards the outletthereof, the improvement for eliminating the hazard of air embolismresulting from expelling entrapped air from said syringe into thevascular system of a patient comprising:

providing the outlet of said syringe in a removable,

transparent, magnifying head;

providing in said head adjacent said outlet, a safety chamberconfigurated such that the plunger of the syringe cannot be advancedthereinto;

filling said syringe with contrast solution;

orienting the syringe with the outlet end up, thereby permitting anyentrapped air to rise towards the outlet;

viewing the contents of said safety chamber through the transparentwalls of said magnifying head to determine whether bubbles of entrappedair are present in said chamber; advancing said plunger towards saidoutlet to expel any entrapped air from said safety chamber bydisplacement while said outlet end is oriented up;

orienting said outlet end down, thereby to permit any remainingentrapped air to rise through said contrast solution away from saidoutlet; and

injecting said contrast solution in accordance with the program of anangiographic procedure with said outlet end pointing down and saidsyringe as nearly vertical as the angiographic procedure permits.

2. The improvement of claim 1 wherein the contrast solution is pouredinto said syringe from the outlet end with the said magnifying headremoved.

3. The improvement of claim 1 including attaching a tube to said outlet;

submerging the free end of said tube in a pool of contrast solution afercontrast solution is poured into said syringe;

expelling entrapped air through said tube by advancing the plungertowards said outlet;

drawing additional contrast solution into said syringe from said poolthrough said tube; and

viewing the contents of said safety chamber through the transparentwalls of said magnifying head to determine whether bubbles of entrappedair remain in said chamber.

i k 8 t

1. In angiography wherein contrast solution is poured into the housingof a power injector syringe and thereafter expelled at a controlled rateby power means advancing the plunger of said syringe towards the outletthereof, the improvement for eliminating the hazard of air embolismresulting from expelling entrapped air from said syringe into thevascular system of a patient comprising: providing the outlet of saidsyringe in a removable, transparent, magnifying head; providing in saidhead adjacent said outlet, a safety chamber configurated such that theplunger of the syringe cannot be advanced thereinto; filling saidsyringe with contrast solution; orienting the syringe with the outletend up, thereby permitting any enTrapped air to rise towards the outlet;viewing the contents of said safety chamber through the transparentwalls of said magnifying head to determine whether bubbles of entrappedair are present in said chamber; advancing said plunger towards saidoutlet to expel any entrapped air from said safety chamber bydisplacement while said outlet end is oriented up; orienting said outletend down, thereby to permit any remaining entrapped air to rise throughsaid contrast solution away from said outlet; and injecting saidcontrast solution in accordance with the program of an angiographicprocedure with said outlet end pointing down and said syringe as nearlyvertical as the angiographic procedure permits.
 2. The improvement ofclaim 1 wherein the contrast solution is poured into said syringe fromthe outlet end with the said magnifying head removed.
 3. The improvementof claim 1 including attaching a tube to said outlet; submerging thefree end of said tube in a pool of contrast solution afer contrastsolution is poured into said syringe; expelling entrapped air throughsaid tube by advancing the plunger towards said outlet; drawingadditional contrast solution into said syringe from said pool throughsaid tube; and viewing the contents of said safety chamber through thetransparent walls of said magnifying head to determine whether bubblesof entrapped air remain in said chamber.